OBJECTIVES: The overall objectives of the project are as follows: 1. Production and serological characterization of rabbit and primate antisera to human T and B lymphocyte associated antigens. 2. Isolation and characterization of the human membrane antigen defined by the above antisera. 3. Immunological studies on experimentally produced (thymectomized and irradiated) T cell deficient chimpanzees. 4. Isolation and characterization of a factor (LAF) released from human mononuclear cells which results in increased thymidine incoporation in human and mouse thymocytes and lymphocytes. BIBLIOGRAPHIC REFERENCE: Gilbertsen, R.B. and Metzgar, R.S.: Human T and B Lymphocyte Rosette Tests: Effect of Enzymatic Modification of Sheep Erythrocytes (E) and The Specificity of Neuraminidase-Treated E, Cellular Immunology 24: 97-108, 1976.